AT72, Shannon Ireland, 2014

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Summary

On 26 February 2014, an ATR 72-202 which had been substituted for the ATR42 which usually operated a series of night cargo flights was being marshalled out of its parking position with a new flight crew on board when the left wing was in collision with the structure of an adjacent hangar. The Investigation found that the aircraft type had not been changed on the applicable flight plan and ATC were consequently unaware that the aircraft had previously been parked in a position only approved for the use by the usual smaller aircraft type.

Description

On 26 February 2014, an ATR 72-202 (EI-FXG) on a scheduled cargo flight from Shannon to Cork at night in normal ground visibility was being marshalled off its parking position when the left wing was in collision with the structure of an adjacent hangar. Damage was caused to the leading edge of the wing and to the steel cladding of the hangar.

Investigation

The event was Investigated by the Irish Air Accident Investigation Unit. It was established that the ATR 72 aircraft involved had been substituting for the ATR43 normally used for the flight and had been positioned empty to Shannon in the early hours of the day of the occurrence by a different flight crew. After arrival, the aircraft had been cleared to taxi to the area adjacent to the East Apron hangar (see the diagram below) where the ATR42 was normally parked and shut down before being towed to the final parking position adjacent to the hangar.

The parking position of the aircraft showing the adjacent hangar. Reproduced from the Official Report.

When the aircraft was ready to depart later that day, the engines were started and, having requested and received taxi clearance from ATC and with a marshaller ahead of the aircraft and a wingman on the left wing, the aircraft began taxiing with the aircraft commander in control, making "a gentle right turn" to pick up the lead-out centreline. Shortly after the aircraft began to move, there was a jolt which the commander reported he had initially thought had been caused by hitting a wheel chock. The parking brake was set, the left engine shut down and the right engine propeller brake set. Once it became apparent that the wing had struck the hangar, the right engine was also shut down and the Cockpit Voice Recorder (CVR) CB tripped in accordance with SOP.

After twenty minutes had elapsed since the crew had acknowledged their taxi clearance and nothing more had been heard from the aircraft, ATC called the Airport Operations Office to check on the status of the aircraft. Six minutes later, the Airport Duty Officer reported back to ATC and only then were the Airport Fire Service (AFS) notified. When the AFS reached the scene shortly afterwards, they found that the damaged aircraft had already been moved into the hangar. Damage to both the aircraft and the hangar was subsequently assessed as being relatively minor.

The aircraft commander's report to the Operator's Safety Office was noted to have included the remark in respect of the time of the collision, "marshaller giving slow right turn hand instructions with no indication to stop or to hasten rate of turn up to striking building". The marshaller's report to their Handling Company employer was noted to have included the statement that "I tried to turn him onto a safe line out but he kept coming straight. [The Wingman] signalled to stop so I stopped him, but he did not stop immediately and he came into contact with the hangar.’’

It was considered that "the confined manoeuvring space made both taxiing the aircraft and the provision of adequate guidance by the Wingman and Marshaller difficult" and that "the prevailing weather and ambient lighting conditions at the time may have contributed to the difficulties experienced by the Flight Crew and Ground personnel".

It was established that a little over 3 years earlier, the Operator has sought to use the stand at the East Apron hangar for their aircraft and had received approval from the Airport Authority to do so for an ATR 42 aircraft subject to the implementation of specified operational safety procedures. These arrangements allowed for the aircraft to be towed/pushed into its parking position and to subsequently manoeuvre off-stand under its own power. The Airport Authority also notified both the Aircraft Operator and the Handling Company used by the Operator that because the ATR 72 was longer and had a bigger wingspan (by 2.48 metres) than the ATR 42, the parking arrangements approved for the ATR 42 adjacent to the East Apron hangar must not also be used by an ATR 72, which would instead be required to park on a main apron stand or be towed into the hangar. It was noted, however, that the Airport Authority did permit the long term parking/storage of one particular ATR 72 aircraft, M-ABEV, adjacent to the hangar. It was noted that the corresponding approval stated that the aircraft "must not be moved under its own power while manoeuvring on the support stand and that all manoeuvring be performed by towing or tractor pushing only".

The Aircraft Operator’s Route Briefing Document was examined and it was found that having referred to the ATR42 being the normal aircraft used, it did not state that the normally used parking position in front of the hangar was only for the use of the ATR 42 and expressly not approved for the ATR 72.

It was noted that the apron where the collision had occurred had been specifically marked to assist the correct positioning and manoeuvring of an ATR42 (see the picture below). A continuous red line marked the protected (safe boundary) area of the aircraft while parked and yellow box makings indicated the location of the main landing gear when parked. There was also a yellow lead-out line marked from the parked position of the nose landing gear which, if followed, would provide approximately 6 metres clearance between the tip of the left wing and the hangar. It was noted that because this lead-out line was set at an angle from the parked aircraft position, it was necessary for an immediate right turn to be made to follow the line and be assured of clearance.

An ATR 42 in the approved parking position showing the apron markings. Reproduced from the Official Report.

The Investigation noted that the greater wingspan of the ATR 72 meant that when parked, its left wing would have been partly over the hatched area and a photograph of the ATR 72 as it had been parked which was provided to the Investigation was found to show the aircraft left main landing gear "well forward and left of the ramp markings to the extent that the nose landing gear extended well beyond the protected area defined by the red line".

The Investigation formally determined the Probable Cause of the Serious Incident was "Collision with a building structure due to insufficient wing-tip clearance for safe manoeuvring in an area that was unsuitable for that aircraft type".

Three Contributory Factors were also identified:

The unsuitability of the parking area for an ATR 72 was not sufficiently promulgated to all personnel concerned in the Operation.

Due to the parked position of the aircraft, adequate clearance between the wing-tip and hangar did not exist when the aircraft commenced its taxi.

The prevailing weather and ambient lighting conditions at the time.

Safety Action was taken by the Aircraft Operator as follows:

The intended addition of a new procedure to their Dispatch Manual to require that in the event of a change of aircraft, any applicable Repetitive Flight Plans must be cancelled and a new plan filed to reflect the change.

A change to the requirements for audit of airport parking areas to require that they are confirmed suitable for both ATR 42 and ATR 72 aircraft (or otherwise).

The Final Report was published on 18 May 2015. No Safety Recommendations were made.